Here it is: http://www.twcenter.net/forums/showt...08#post8727508
You are right you have to change all factions one by one in startpos.esf. The right location for that is in victory conditions (CAMPAIGN_PREOPEN_MAP_INFO in startpos). It is not to much work if you can use Taw's esf2xml tool.
You feel right about it. Messing with Turns Per Year/Month can cause series problems to AI (passive behaviour).P.S.
I prefer to change the ending date as the UI is so integrated with the one-turn-is-two-weeks system (saying Early MONTH and Late MONTH) that I feel screwing with the Turns Per Year/Month can only end in tears.